About fluorescence correlation spectroscopy will be explained hereinafter as an analysis example of fluctuation of fluorescence that is an example of light emission. Fluorescence correlation spectroscopy has been discussed in “Fluorescence Correlation Spectroscopy” R. Rigler, E. S. Elison (eds.) Springer (Berlin), “Protein, Nucleic Acid, Enzyme” (1999) Masataka Kinjo Vo. 44, No, p1431-1437, and PCT National Publication No. 11-502608. An apparatus for fluorescence correlation spectroscopy is often manufactured on the basis of a confocal optical microscope. A confocal optical microscope has been discussed in “Confocal Microscopy” T. Wilson (ed.) Academic press (London). A laser scanning confocal optical microscope that is a kind of confocal optical microscope may be used as a basis. A laser scanning confocal optical microscope has been described in Japanese Patent Laid-Open Publication No. 10-206742. When an apparatus for fluorescence correlation spectroscopy is combined with a confocal optical microscope, statistic analysis operation such as correlation spectroscopy can be performed while observing or recording a fluorescent microscopic image.
PCT National Publication No. 2003-524180 discloses the switching of a fluorescence correlation spectroscope (FCS) and a laser scanning microscope (LSM) in a fluorescence detecting apparatus and method.